The present invention relates to miter gages of the type adapted for use with power tool work tables and, more particularly, miter gages for use with power saw tables for holding a workpiece at a predetermined orientation for feeding into the saw blade extending through the saw table.
A miter gage is a device commonly used in combination with a table saw or band saw and is used to hold a workpiece during a crosscut operation. Such a miter gage typically includes an elongate bar which is shaped to slidably engage a groove formed in the tabletop of the saw table and extends in a direction parallel to the cutting plane of the tool mounted beneath the saw table. A protractor is mounted on the bar such that it pivots about a vertical axis and includes a flat face for engaging a workpiece.
To perform a crosscutting operation with such a miter gage, the workpiece is held against the face of the protractor and the miter gage is slid along the groove past the tool, which may be a rotating circular saw blade for a crosscutting operation, and the workpiece is cut by the tool. To perform a miter cut, the protractor portion of the miter gage is pivoted such that the workpiece-engaging face is disposed at the desired skewed or nonperpendicular angle to the plane of rotation of the tool. Consequently, a workpiece held against the face of the protractor and fed into the rotating saw blade is cut to have a beveled or angled end.
The better quality miter gages also include a work holding assembly which forms a part of the miter gage. For example, the Goldschmidt U.S. Pat. No. 2,759,503 shows a miter gage having a clamp in the form of a vertically adjustable lock rod which is supported by a lock guide extending outwardly from a grip mounted on the protractor. The lock rod comprises a threaded shaft having a disk-shaped shoe mounted on its lower end. The lock guide includes an elongate opening sized to receive an upper end of the lock rod and the elevation of the lock rod relative to the lock guide is adjusted by a pair of nuts threaded on the lock rod and positioned above and below the lock guide.
To adjust the elevation of the lock rod relative to the lock guide and thereby position the shoe at a predetermined height above the saw table, the nuts are displaced along the shaft of the lock rod away from the lock guide to allow the lock rod to be moved vertically relative to the lock guide. The lock rod may also be displaced relative to the lock guide by sliding the lock rod within the elongated opening. Once the lock rod is positioned at an appropriate elevation and location along the opening, the nuts are tightened against the upper and lower surfaces of the lock guide and thereby hold the lock rod in position relative to the lock guide.
To facilitate the rapid clamping and unclamping of the lock rod against a workpiece, the lock guide is attached to the lock lever which is pivotally attached to the grip and is linked to a trigger. By squeezing the trigger against the grip, the lock lever pivots relative to the grip and thereby moves the lock guide and lock rod slightly downwardly, thereby clamping a workpiece between the shoe and the saw table. The trigger is spring actuated such that when the grip is released from the hand of a user, the lock lever pivots the lock guide slightly upwardly so that the shoe is removed from engaging the workpiece.
While the aforementioned miter gage provides a safe and secure means for clamping a workpiece against the face of the protractor, the procedure for vertically adjusting the lock rod to accommodate workpieces of varying thicknesses is slow and relatively tedious. Four distinct operations must be performed: the upper and lower nuts must be individually moved away from the lock guide to allow the vertical movement of the lock rod, and the nuts must again be individually displaced against the lock guide to secure the lock rod once the lock rod has been positioned at the proper elevation.
Accordingly, there is a need for a miter gage having a work holding assembly in which the work holding piece may be adjusted in elevation to accommodate workpieces of differing heights in a rapid and easy manner. Furthermore, the workpiece engaging device must be relatively inexpensive to manufacture and reliable in operation.